Method of cutting curved-tooth gears



Jan. 13, 1931. H. E. STONEBRAKER I 1,788,639

' METHOD OF CUTTING CURVED TOOTH GEARS I Filed March 22, 1928 INVENTOR Patented Jan. "13, 1931 HAROLD E. sronEBRAKEaoF eoonnsrnn miw You I METHOD-F cur'rrnecunvungroorfica ms i Applicatioiz'filed March 22,1928. SerialNo.2 63,9Q6.i

" 1 9 j, g I I v by the cutting edge of a tool.

This invention relates to curved tooth gears, or what are sometimes commercially termed spiral orcircular gears, and'has for one of its objects to {produce a lengthwise fi-curv'ed tooth of the samecross-secgtion and strengththroughout its length,- and with. faces of uniformly smooth-"and, accurate f; V'finish, resulting in a :gear of" greater ef- 7 ficiency and more quiet inoperation than, I 10 those heretofore in general use. a

7 One general practice in ,cuttlng curved,

tooth gears has been to rotatet'an annular v face .mill about an axis perpendicular to a plane tangent to the pitch, surface of the 1 gear and in order? to obtain the desired in clination of tooth face, the cutting edge of the tool is correspondingly inclined'. to the. Y aXis of rotation. of the cutter head." Consequently, the cutting edge sweeps out a coni- 0 cal surface, and the tooth surfaces are i therefore sections of cones, i i This practice has certain disadvantages,

I, among which is that a tooth so? produced varies infcross-sectionbetween its? ends, so that its strengthYand the bearing qualities of its faces are likely tovary at different I points lengthwiseof the tooth. In such a geaigthetooth face hearing may be; good at p r the center and poor at the-ends, and such de- Q ficlencies qulckly cause a gear to wear and become noisy.

One of the virtues of a curved tooth gear is overlap-fof the teeth, resulting in quieter action, and the desired ideal is to secure this along with other advantages of the curved Y tooth gear, and at the same time retain'the uniform bearing and strength characteristics ofthe straight tooth gear, factors which cannot be had where a conical section is formed More particularly, the object of the invention is to" bring about these desired results by producing a gear in which the tooth faces are parts of cylindrical sections rather 745' thanconical sections; Thecylindrical sectionis produced byf maintainin the cutting edge, parallel to the axis about 'which it travels arcuat'ely." Where the cutting edge e is thus held parallel to the axis of movement 7 ofthe cutter, a'finer', smoother, and more acpointed; out inthe claims. In th ydm i Figure 1 is a plan view O Portibfl'df 651K curatesurfaceiisproducedthan Where differ ,entparts of thecutting edge are at difl'erent' distances from the axis about -which' the cutter -moves, aswhere a conical'section'is I cut" by*thelconventional" face} mill 1 cutter 255 heretofore employed, in: producing; curved tooth-gears. Q 5- v 1 The invention coinprehends certain other objects and advantages;;al l "of which will appear from the Y following description when read in conjunctionwith the accompany n'g drawings, the novel features being a pinioninade according to the inventiori I i. F gure-2 1s a sectional 'VlGW- illustrating? OIIBiPQSSlblB disposltlon of cutter for'pro- 'ducing onetooth faceonone'side of atooth 3 Figure 31s asimilarviewillustrating:thev

disposition of :acutter for; producingvthe" opposite tooth face onthe other sideoft-he 'toothspace. 1

i The invention herein disclosed is l i bletohuitvedtoOth gears, generally, either of", the spur type which is :illustrated or of the bevel type, or 'whereverfa lengthwise curved tOOtllyiS desirable, andthefprinciple .isap plicable and intended to be used in cutting mvoluteor; generated gears, where a relar tive rolling motion takes place between the gear: blankfand cutter-during the cutting operation, as well understood in the gear manufacturingart, I

In-"theconstruction 'llu's'trated, fl desig nates a portion of a spur gearand 2 is a tool. shown mounted upon a cutter 3 and travelling in a tooth space orgroove between adjacentteeth 4 and 5. The cutter 3''may I rotate about "the axis'6, and-7 designates Vthe'cuttingedgeof the tool whichengages I V the adjacent surface ofthe tooth 5gandis i,

parallel to the IaXisG -about .which the cutter travels. Thus the cutting edge 7 of thetool I sweeps out a cylindricalsurface on the tooth so thatpthe tooth face is'composed of;e1e ments of aicylinder,resulting in a uniform toothcross-sectionfroniend to end and uniform inclination of the tooth face.

The tooth face 8 on the opposite side of the tooth space would be produced by another cutter arranged as shown in'Figure 3 with itscutting edge 9 parallelto the axis 10 about which the cutter travels. The radius A, Figure 2, whichdetermines'the arc of travel of the cuttin edge 7 that forms the face on tooth 5, is the. same as radius B, Figure 3,,which determinestae arc oftravel of cutting edge 9 that formstheaad: jacent face 8 on tooth 4. In thisn anner are produced teeth and" spaces definedby faces having the same curvature andicorrn prising a similar section of the same cyliri der. c- 7 ,lVhile a particular cutter has been shown for purposes ofexp'lanation, itwillbe understood that agear embodying. the invention may be cut :witlra'continuously rotating cutter or with an oscillating cutter, and it is alsoewithinv the 'province of the invention to use. two cutters operating. on: two tooth ther types of; cutfaces at the same time.

ters. may beused. and.. difterent rocedure followed without departing from t e under lying novel features of the improvement, and

this application .is. intended to cover any modificationsor adaptat10ns1 c0.m1ng wltli n the spirit of the invention, or the scope of the following claims. I claim: 7

1.1 The; method of cutting 'a. gear: having teeth that are curved endwiseacross the gear face, consisting in moving atoolin an arcuate path ..-across the gear face, saidgtool i having a straight cutting edge arranged parallel to the axis about which the tool travels, and acting a to produce a cylindricallike L surface.

2. The method of cutting a gear: ha ving teeth that arev curvediendwise across the gear face, consisting in producing adjacent faces by moving two-tools about different axes arranged angularly to each:.other, said:- tools having straight cutting edges arranged:

parallel to. thev axes about which they move and acting to sweep out: cylindrical-likesurfaces.

3. Themethod ofxcutting a gearhaving teeth that are curved endwise across the gear: face, consisting in producing. adjacent-"facesby moving two different; tools in different curved paths. across the gear face and about diiferent axes arranged angularly; to. each: other, each cutting tool having. a cutting. edge .inv parallel relationship. to. the axis about which thetool travels.

signed my name. i

HAROLD. E.; STONEBRAKERE In witness whereof, I; have hereunto.- 

